This invention claims the benefit of priority to Korean Patent Application No. 2001-1245 filed Jan. 10, 2001 and Korean Patent Application No. 2001/8970 filed Feb. 22, 2001. The present invention relates to a contact of substrates of a touch panel, and more particularly, to a method of bonding the substrates in order to embody optimal design thereof by reducing an inactive area on the touch panel and a contact structure of a flexible printed cable (FPC) for applying external signals to the touch panel.
A personal computer, a portable transmitter, a personal digital assistant and the like perform text and graphic processing by using various input devices such as keyboard, mouse and digitizer.
In particular, the digitizer is a device for digitally detecting positions of the fingers or pens on a specifically manufactured flat panel and outputting their values in the form of X/Y coordinates. The digitizer has an advantage that it can input characters or figures more conveniently and precisely than the mouse, keyboard, scanner and the like. Among the digitizer, a touch panel has frequently been used for an electronic note or the personal digital assistant (PDA).
As shown in FIG. 1, a digitizing apparatus, which can perform various functions of screen motions on a display 10 by attaching a touch panel 20 to a front surface of the display 10, is a typical type of a graphic user interface (GUI). The touch panel can be divided into a resistive type, a capacitive type, an ultrasonic wave type, an optical (infrared) type, an electromagnetic induction type and the like, according to operating methods thereof. Such various touch panels have features that signal amplification, resolution, difficulty in design and manufacturing techniques, and the like can be varied according to the operating methods thereof. The operating method of the touch panel can be selected according to its durability, its economical efficiency, etc. in addition to its optical property, its electromagnetic property, its mechanical property, its environmental resistance, its input property, etc.
The resistive touch panel has been combined with a liquid crystal display (LCD) and widely spread as an input device for use in the electronic note, the PDA, the portable personal computer, etc. Its design is very advantageous as compared with the other types of the touch panels, in view of thinness, compactness, lightness, low power consumption, etc. There are matrix and analog methods as a detection method of the resistive touch panel. Further, 0.1xcx9c0.2 mm thick film substrate, 0.2xcx9c2.0 mm thick glass substrate and 1.0xcx9c2.0 mm thick plastic substrate can be used as a transparent electrode, and upper/lower electrodes are constructed by combining these substrates. The analog detection method is again divided into 4-wire type, 5-wire type, 8-wire type, etc. according to electrode wiring.
FIG. 2 is a schematic view of the resistive touch panel 20. The resistive touch panel is constructed by fabricating transparent conductive films 50 on a first substrate 30 for forming the upper electrode and a second substrate 40 for forming the lower electrode, respectively, and then by fabricating dot spacers 60 for electric insulation between the first and second substrates 30, 40 on the conductive film 50 of the second substrate 40. In the resistive touch panel, distribution of the signals on X/Y coordinates by means of the two substrates is calculated and is in turn sent to external driver soft through a connector. Further, the touch panel is divided into the 4-wire, 5-wire, 8-wire types according to the number of bus lines for recognizing the signals on the X/Y coordinates of the substrates. Consequently, characteristics of a recognition or signal processing method of the signals distributed on the X/Y coordinates can be varied according to the number of the bus lines.
FIGS. 3(a) and (b) show the 4-wire resistive touch panel 20, in which an insulating layer is processed and placed between the first substrate 30 and the second substrate 40.
As shown in FIG. 3(a), in order to form an active area a1 made of high resistive metal, X-axis potential compensating electrodes 60a, 60b made of low resistive metal are arranged in two lines on both lateral sides of the transparent conductive film 50 of the second substrate 40, after the insulator layer has been formed on the substrate. Further, dot spacers 60 made of insulating material for electric insulation between the two substrates, i.e., the first substrate 30 and the second substrate 40, are formed within the active area a1 defined by a space between the potential compensating electrodes 60a, 60b. 
As shown in FIG. 3(b), in order to form an active area a2 made of high resistive metal, Y-axis potential compensating electrodes 70a, 70b made of low resistive metal are arranged in two lines on both lateral sides of the transparent conductive film 50 of the first substrate 30, after the insulator layer has been formed on the substrate.
Flexible printed cables (FPC) 80 for applying external signals to the touch panel 20 are connected to the first and second substrates 30, 40.
Before the first and second substrates 30, 40 are bonded together to FPC contacts 81 formed thereon, an electrical signal path made of conductive material is formed in order to apply the electric signals to the first substrate 30. After the FPCs 80 have been contacted to the FPC contacts 81 of both substrates, the second substrate 40 for sensing the X coordinate and the first substrate 30 for sensing the Y coordinate are bonded together in a state where the transparent conductive films 50 face each other. The X-axis and Y-axis potential compensating electrodes 60a, 60b; 70a, 70b, which are formed, respectively, on the first substrate 30 and the second substrate 40, are gathered on one side of the insulator layers 31, 41. Further, each of the first and second substrate 30,40 has a predetermined FPC contact 81 for bringing the substrates into contact with the FPC 80.
The FPC contact 81 of the second substrate 40 comprises of a pattern that protrudes from the X-axis potential compensating electrode 60a by an arbitrary length (inactive area) L1; and another pattern that extends along an outer periphery of the active area a1, is then bent, and further extends from the other X-axis potential compensating electrode 60b disposed parallel to the pattern. When the two substrates 30, 40 disposed parallel to each other are combined together by causing them to be disposed within the area having the arbitrary length L1 formed by the FPC contacts 81, it is constructed such that the other pattern, which abuts against the FPC contact 81 of the first substrate 30, is also disposed in parallel. Therefore, the patterns of the second substrate 40 have configurations that they protrude from the insulator layer 41 to the outside by an arbitrary length.
The contact 81 of the first substrate 30 has a configuration that patterns, which are gathered from each end of the Y-axis potential compensating electrodes 70a, 70b toward a central portion of the first substrate, protrude to the outside by an arbitrary length L2.
The contact points formed by respective FPC contacts 81 of the first substrate 30 and the second substrate 40 will be described according to the bonding process of the first substrate 30 and the second substrate 40. When the first substrate 30 is put over and combined with the second substrate 40, the pattern of the first substrate 30 comes exactly into contact with that of the second substrate 40. Thus, the first and second substrates 30, 40 can form the contact which the FPC 80 for applying the external signals via the FPC contact 81 gathered at one point can be contacted.
In order to detect the X coordinate in the aforementioned constitution, by applying a potential to the second substrate 40 through the FPC contact 81 disposed thereon, the potential is distributed on an entire surface of the transparent conductive film thereof. When the first substrate 30 has been in contact with the second substrate 40 by means of pressure exerted on a surface of the touch panel, the potential at that point is induced to the opposite first substrate 30. At this time, the signal is read into the FPC contact 81, and the X coordinate is then calculated. While the first substrate 30 is in contact with the second substrate 40 in this way, a potential for detecting the Y coordinate is also applied to the first substrate 30, and thus the potential is distributed on an entire surface of the transparent conductive film thereof.
Likewise, the Y-axis potential at a point where the pressure is applied is induced to the second substrate 40 and is received through the FPC contact 81. Then, the Y coordinate is calculated by using a signal corresponding to the received potential. Finally, the values obtained from the calculation of the X/Y coordinates are shown on the display.
In such a case of the 4-wire resistive touch panel in which by using a single FPC 80, the potential is applied to the second substrate 40 through the FPC contact 81 and the X/Y coordinates are simultaneously recognized, the FPC contact 81 should be disposed on each of the two substrates. Thus, the inactive area, i.e., a pattern area (a minimal area for arranging the pattern) protruding to the outside by a length L1, must be expanded.
Furthermore, since the signals are applied through conductive material filled between the first and second substrates in the resistive touch panel, it is substantially likely that shock to the two substrates and dislocation thereof cause the contact patterns to be dislocated and result directly in inferiority of the contact. Therefore, there was a problem in that reliability of the products would be deteriorated.
An object of the present invention is to expand an active area between the two substrates, i.e., first and second substrates of a resistive touch panel.
Another object of the present invention is to reduce an inactive area, which is formed by (flexible printed cable) FPC contacts and signal contacts of the first and second substrates of the resistive touch panel, in order to reduce a compensating electrode area.
A further object of the present invention is to provide a substrate bonding method wherein an inactive area, which is formed by FPC contacts and signal contacts of first and second substrates of a resistive touch panel, can be reduced and positions of the FPC contacts on the touch panel can also be changed.
According to an aspect of the present invention for achieving the above objects, there is provided a contact structure for use in a touch panel including a first substrate having a transparent conductive film in which an active area is defined by symmetrically providing X-axis (Y-axis) potential compensating electrodes made of low resistive metal thereon at an arbitrary interval, a second substrate bonded together to the first substrate and having a transparent conductive film in which an active area is defined by symmetrically providing Y-axis (X-axis) potential compensating electrodes made of low resistive metal thereon at an arbitrary interval, dot spacers filled between the two substrates so as to ensure electric isolation between the first and second substrates, and contacts concentrated on a flexible printed cable (FPC) so as to form an electrical signal path out of conductive material when the two substrates are bonded together. The contact structure comprises a FPC contact which is constructed at an arbitrarily selected point on electrode arrangement defined by the X-axis (Y-axis) potential compensating electrodes arranged on the transparent conductive film of the first substrate along outermost edge portions thereof; and another FPC contact which is bonded to the FPC contact on the first substrate and is constructed at an arbitrarily selected point on another electrode arrangement defined by the Y-axis (X-axis) potential compensating electrodes arranged on the transparent conductive film of the second substrate along outermost edge portions thereof.
According to another aspect of the present invention, there is also provided a contact structure for use in a touch panel including a first substrate having a transparent conductive film in which an active area is defined by symmetrically providing X-axis (Y-axis) potential compensating electrodes made of low resistive metal thereon at an arbitrary interval, a second substrate bonded together to the first substrate and having a transparent conductive film in which an active area is defined by symmetrically providing Y-axis (X-axis) potential compensating electrodes made of low resistive metal thereon at an arbitrary interval, dot spacers filled between the two substrates so as to ensure electric isolation between the first and second substrates, and contacts concentrated on a flexible printed cable (FPC) so as to form an electrical signal path out of conductive material when the two substrates are bonded together. The contact structure comprises X-axis (Y-axis) potential compensating electrodes arranged along outermost edge portions of the transparent conductive film of the first substrate; a FPC contact for the first substrate, which is constructed at an arbitrarily selected point on electrode arrangement defined by the X-axis (Y-axis) potential compensating electrodes arranged on the transparent conductive film of the first substrate; Y-axis (X-axis) potential compensating electrodes arranged along outermost edge portions of the transparent conductive film of the second substrate; another FPC contact for the second substrate, which is constructed at an arbitrarily selected point on electrode arrangement defined by the Y-axis (X-axis) potential compensating electrodes arranged on the transparent conductive film of the second substrate; an insulator layer having an arbitrary length which is formed along the X-axis and Y-axis potential compensating electrodes around the FPC contacts constructed, respectively, on the potential compensating electrodes of the first and second substrates; and a low resistive metal layer in which the FPC is attached to an upper layer portion of the insulator layer formed on the potential compensating electrodes.
According to a further aspect of the present invention, there is also provided a contact structure for use in a touch panel including a first substrate having a transparent conductive film in which an active area is defined by symmetrically providing X-axis (Y-axis) potential compensating electrodes made of low resistive metal thereon at an arbitrary interval, a second substrate bonded together to the first substrate and having a transparent conductive film in which an active area is defined by symmetrically providing Y-axis (X-axis) potential compensating electrodes made of low resistive metal thereon at an arbitrary interval, dot spacers filled between the two substrates so as to ensure electric isolation between the first and second substrates, and contacts concentrated on a flexible printed cable (FPC) so as to form an electrical signal path out of conductive material when the two substrates are bonded together. The contact structure comprises an insulator layer having an arbitrary length which is formed along the X-axis and Y-axis potential compensating electrodes around the FPC contacts constructed, respectively, on the potential compensating electrodes of the first and second substrates; and a low resistive metal layer in which the FPC is attached to an upper layer portion of the insulator layer formed on the potential compensating electrodes.
According to a still further aspect of the present invention, there is a method for bonding substrates of a touch panel fabricated by processes of forming insulator layers on first and second substrates, forming potential compensating electrodes out of low resistive metal on transparent conductive films, forming dot spacers out of insulating material within an active area so as to achieve electric insulation between the first and second substrates, connecting a flexible printed cable (FPC) to the first and second substrates so as to apply signals to the touch panel from the outside, and bonding the first substrate for detecting an X coordinate and the second substrate for detecting a Y coordinate together so that the transparent conductive films can face each other. The method for bonding the substrates of the touch panel comprises the steps of forming the potential compensating electrodes out of the low resistive metal on the transparent conductive films upon completion of a process of depositing an insulator layer onto the first and second substrates, and forming an insulator layer around flexible printed cable (FPC) contacts formed on the potential compensating electrodes of arbitrarily selected one of the first and second substrates so as to arbitrarily change positions of the FPC contacts with respect to the potential compensating electrodes; forming a new low resistive metal layer, to which FPCs will be attached, on the insulator layer so as to connect the FPC to the potential compensating electrodes of the substrates; forming dot spacers out of insulating material within the active area so as to achieve electric insulation between the first and second substrates between which the insulator layer and the low resistive metal layer are formed through the above steps; connecting the FPC with a band region formed by the insulator layer and the low resistive metal layer, in order to apply signals to the first and second substrates from the outside after the insulator layer, the low resistive metal layer and the dot spacers have been formed between the first and second substrates through the above steps; and bonding together the first substrate for reading an X coordinate and the second substrate for reading a Y coordinate so that the transparent conductive films can face each other, after the connection between the insulator layer, the low resistive metal layer, the dot spacers and the FPC, which are sequentially formed through the steps, has been completed.
In a case where the substrate contact of the resistive touch panel is constructed as such, the signal contacts are formed in the two substrates for constructing the upper and lower electrodes. Thus, the inactive area is remarkably reduced while the active area is increased. From the viewpoint of the constitution of the touch panel, dislocation of a contact band can be greatly reduced, and contact stability that contact deformation due to the external shock is hardly produced can be obtained. Further, since the FPC contacts are fabricated according to the bonding method of the present invention, optimum design of the touch panel including the arrangement of the potential compensating electrodes for expansion of the active area can be realized and a degree of freedom of the FPC contact positions for the external signal application can be kept large. Further objects and advantages of this invention will be apparent from the following detailed description of presently preferred embodiments which are illustrated schematically in the accompanying drawings.